In recent years, many digital AV devices such as DVD players, digital set-top boxes, digital television broadcasting receivers and AV amplifiers are used in, for example, homes. In order to make it possible to freely set up these digital AV devices at arbitrary locations in a home and to transmit contents from one of the AV devices to the other AV devices, there is proposed a technique for wirelessly connecting a plurality of AV devices via a wireless network.
FIG. 15 is a block diagram showing an example of an IEEE 802.15.3 network using an UWB (Ultra Wide Band) according to a prior art. Referring to FIG. 15, devices 101 to 104 are components of the IEEE 803.15.3 network, and form one piconet 100. In this case, the device 101 is referred to as a piconet coordinator (PNC), and functions as a master device of the piconet 100.
In addition, FIG. 16 is a timing chart showing an example of a bandwidth allocation method for packet communication in the piconet 100 of FIG. 15. In the packet communication in the piconet 100, a frame format called super frame is used. Referring to FIG. 16, each super frame has a super frame period Tsf. Further, each super frame is constituted, from top, by three periods of a beacon period Tb, a contention access period (CAP) Tcap, and a contention free period (CFP) Tcfp. Each of the three periods includes at least one time slot having a predetermined time period. In this case, the beacon period Tb is secured in order to transmit a beacon signal from the device 101 of the PNC to the other devices 102 to 104. In the beacon period Tb, the device 101 generates a beacon signal, which includes control data for synchronizing start timings of super frames for the devices 101 to 104 with one another and control data such as data related to time slots for transmission of data among the devices 101 to 104, and transmits the beacon signal to the devices 102 to 104. In addition, the contention access period Tcap is used so that the devices 101 to 104 transmit asynchronous data to the entire piconet 100. Further, the contention free period Tcfp includes a plurality of time slots and is used to transmit data between one source device and at least one sink device selected from among the devices 101 to 104.
FIG. 17 is a sequence diagram showing a method of transmitting AV stream data in the piconet 100 of FIG. 15. Referring to FIG. 17, the device 103 of a source device (referred to as a source device 103 hereinafter) transmits AV stream data to the device 102 of a sink device (referred to as a sink device 102 hereinafter). First of all, the source device 103 acquires data on a plurality of video output formats and audio output fat mats of video and audio, which the sink device 102 can receive and reproduce, from the sink device 102. For example, when the sink device 102 is a digital television broadcasting receiver, the source device 103 acquires the data on a plurality of video output formats and audio output formats of video and audio, which the digital television broadcasting receiver can receive and reproduce, by previously reading out EDID (Extended Display Identification Data) stored in the sink device 102. Next, the source device 103 selects a video output format and an audio output format of AV stream data transmitted to the sink device 102 from among the acquired video output formats and audio output formats. Then, the source device 103 requests the device 101 of the PNC to reserve a bandwidth required to transmit the AV stream data to the sink device 102 based on the selected respective formats. In response to this, the device 101 performs a time slot allocation process (also referred to as a scheduling) for transmitting the AV stream data from the source device 103 to the sink device 102, and notifies the source device 103 of data on allocated time slots using a beacon signal. Then, the source device 103 transmits a signal for notifying the sink device 102 of the selected video output format and audio output format to the sink device 102, and transmits the AV stream data to the sink device 102 at timings of the notified time slots. Finally, each of the source device 103 and the sink device 102 requests the device 101 to release the reserved bandwidth. In response to this, the device 101 notifies the source device 103 and the sink device 102 of control data indicating an end of transmission of the AV stream data using a beacon signal. As described above, in the IEEE 802.15.3 network, the AV stream data can be transmitted from the source device 103 to the sink device 102. For example, Patent Document 1 and Non-Patent Document 1 describe other methods of transmitting AV stream data.    Patent Document 1: Japanese patent laid-open publication No. JP-2006-270248-A.    Non-Patent Document 1: High-Definition Multimedia Interface Specification Version 1.3a, November 2006.